Drinking Water and Biological Contaminants Science Fair Projects

Methods/Materials

Materials
Residential and environmental water samples,Colorimetric culture media(Readycult Coliforms),Kovacs indole reagent,MacConkey agar plates,Glass sample vials with caps,Transfer pipettes,UV long wave light source,Bacterial Incubator,Positive control:Laboratory strain E. coli

Procedure
.Collect 10 mL water samples from a variety of sources.
.Immerse a 10 microliter inoculating loop into the water sample and spread it on the MacConkey plate by streaking. Check for bacterial growth on the plate after 24 hour incubation at 37°C.
.To each sample add Readycult colorimetric culture media and incubate as above
.A color change to green-blue color indicates presence of coliforms.
.Blue florescence under UV light indicates presence of E. coli.
.Add a few drops of the Kovacs reagent to the top of the sample and look for a red ring to confirm E. coli presence.

Results

Tap water did not undergo the blue-green color change in the Readycult Coliforms media nor did it fluoresce under UV light. These samples also did not produce a red ring in the indole test. Thus, tap water was free of bacterial contamination. In contrast, run off-water as well as water from community lakes produced a blue-green color in Readycult media, fluoresced under UV light, and produced a red ring in the indole test, suggesting E. coli presence. Water samples from the ocean remained yellowish in the colorimetric media but did not fluoresce under UV light.

Conclusions/Discussion

Drinking (tap) water in my home is free from bacterial contamination. Water samples from lakes and bays were consistently unsanitary and usually contaminated with fecal matter. Ocean water was cleaner in that it did not have any fecal coliforms. 3rd party contributor